(a) Field of Disclosure
The present disclosure of invention relates to a display device, and more particularly to a layout structure of an integrated display device having a driver circuit monolithically integrated in a display panel thereof.
(b) Description of Related Technology
As one of widely used image display devices, the liquid crystal display (LCD) device is one that generally includes two display panels each provided with field controlling electrodes such as pixel electrodes and a common electrode. A liquid crystal material layer is typically interposed between the two display panels. The LCD device displays images when voltages are applied to the field-generating electrodes to thereby generate corresponding electric fields in the LC layer, where the electric fields determine orientations of LC molecules therein and thus selectively adjust polarizations of incident light rays which polarized light rays are then further processed to form a desired image. As examples of display devices other than LCD ones, there are organic light emitting devices (OLEDs), plasma display devices, and electrophoretic display devices.
The LCD display device generally includes a display panel (a.k.a. TFT panel) including pixel units each with a respective switching circuit element (e.g., a thin film transistor or TFT), display signal lines, a gate driver that supplies gate signals to gate lines among the display signal lines so as to turn on/off desired ones of the switching circuit elements, a data driver for applying data voltages to data lines among the display signal lines, and a signal controller for controlling the above circuit elements.
The gate driver and the data driver circuits may be provided as individual IC chips mounted on the display device, or they may be mounted on a flexible printed circuit film as a tape carrier package (TCP) type and attached to the display device, or they may be mounted on a separate printed circuit board (PCB). Alternatively and particularly, the gate driver circuit may be monolithically integrated as part of the TFT display panel by forming the gate driver circuit with the same fabrication process steps as used for forming the display signal lines and the switching circuit elements (the TFTs).
When the gate driver circuit is thus directly integrated in the display panel, the circuit elements of the driver may be formed by a photolithographic patterning method using an exposure step and a developing step. Here, it is sometimes the case that a difference is present within the physical layout of various features (e.g., circuit elements) of the device so that some areas of the layout have finely pitched features (e.g., conductors with very narrow line widths) and other areas of the layout have less finely pitched features (e.g., conductors or electrodes with much larger line widths or alike dimensions). In other words, when the integrated circuitry is fabricated (by mass production means) the relative packing densities of neighboring circuit elements among the several circuit elements in the integrated circuit layout can be substantially different. More specifically, when the gate driver circuit is patterned, different portions thereof can have substantially different line or electrode widths or alike dimensions and the difference in respective pattern densities may influence patterning of the circuit elements, especially those having a relatively large patterning density (e.g., tightly packed and finely pitched layout features) as opposed to those having a substantially smaller patterning density (e.g., less tightly packed and more coarsely dimensioned or pitched layout features). For example, when a first circuit element having a relatively simple concentrated pattern such as that of a capacitor plate or electrode is disposed adjacent to other circuit elements having relatively complicated and finely pitched layout patterns such as gate and source electrodes of MOSFET transistors, a difference of concentration of a developing solution used when developing a corresponding photosensitive film (PR layer) after photolithographic exposure may cause overdevelopment (e.g., excessive etching) of the photosensitive film in areas where the other (finely pitched) circuit elements are provided and their more complicated patterns are disposed near the boundary portion between the different first and other patterns. Thus, the patterning of the finely pitched circuit elements of the driver circuit may be deteriorated such that a defect of the driver may be generated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that is not pre-recognized by and does not form part of the prior art that is already known to persons of ordinary skill in the pertinent art.